When an option of a product A (let's say the option: XL size) has zero quantity, and you choose on the side filter on that size, it brings me the product A as a result!

Try and you will see. Set an option to zero quantity with subract set to yes and open the category view. Choose the option that you know you have zero quanity on a specific product and check the filtered products. The one with zero quantity will be there!